Plasticized sponge material and method of making same



Patented Dec. 29, 11953 P-LA STICIZED SPO METHOD OF NGE MATERIAL ANDMAKING SAME Christopher Lumley Wilson, Columbus, Ohio No Drawing. Aplication September 19,1949, Serial No. 116.643 '2. Claims. (Cl.117-138.8)

"This invention relates to a sponge material comprising partiallyformalized polyvinyl alcohol, and relates particularly to such a spongematerial having incorporated therein a plasticizer' to maintain thesponge in a soft and resilient condition.

Sponge and expanded materials comprising partially formalized polyvinylalcohol and their preparation are described in my copending applicationSerial No. 29,657, filed Mayz l, 194$,and now Patent No. 2,609,347,which is a continuation-impart of my prior copend'ing application SerialNo. 769,537, filed August 19, 1947, now abandoned. These spongematerials are prepared by reacting the formaldehyde with polyvinylalcohol so that only a portion of the hydroxyl groups of the alcoholenters into the reaction. Preferably the solution of the materials isexpanded as by beating air into the solution and the reaction is thenpermitted to proceedso that a solid is formed containing openingsformerly occupied by the bubbles of air or other gas. is employed inorder to speed up the reaction.

As further set forth in the above mentioned Patent 2,609,347, the spongematerials described therein are made by a process comprising providingan aqueous solution of formaldehyde, polyvinyl alcohol containing lessthan residual hydrolyzable material in the moleculean acid catalyst inwhich the acid functional group is inorganic and having a dissociationconstant of at least 10- and a froth-stabilizing wetting agent solublein and substantially stable to said solution; forming a substantiallystable and homogeneous froth withsaid solution stabilized with thewetting agent; reacting the polyvinyl alcohol and the formaldehyde inthe solution thereby causing gellation and solidification of the frothwith the production of interconnected pores simultaneously with theprogression of the" reaction, the froth being formed prior toappreciable reaction between the polyvinyl alcohol and the formaldehyde;and stopping the reaction when approximately 35-80% of the hydroxylgroups of the polyvinyl alcohol have beenreacted with the formaldehyde.I

Sponge materials prepared in the above mannor are soft and resilientwhen" they contain appreciable amounts of water. When the spongematerials become dry, however, they shrink to a certain extent andbecome hard and rigid. They are immediately softened as soon as water isre introduced into the sponge material. Although this re-wetting of thesponge material immediately changes it from a rigid solid to a resilientIn the preferred procedure, an acid catalyst elastic material and thedrying out of the material causes no deleterious eifects, the dry spongematerial does not have as pleasing an appearance to the prospectivepurchaser.

I have discovered that the sponge material may be maintained soft andresilient if a plasticizer is incorporated therewith. These plasticizersare polyethylene glycols and polyalkanolamines and may be introduced bysoaking the sponge material in either the heated plasticizer or in anaqueous solution of the plasticizer. After soak ing in the liquid, theexcess liquid. is removed. These plasticizers, which are preferablyliquid at ordinary room temperatures, maintain the sponge material in asoft, resilient condition.

One of the features of this invention is to provide a method of making asoft, resilient sponge material comprisingproviding a partiallyformalized polyvinyl alcohol sponge and soaking the sponge in a liquidincluding a member of the class consisting of polyethylene glycols andpolyalkanolamines; another feature of this invention is the provision ofa partially formalized polyvinyl alcohol sponge material containing as aplasticizer a member of the class consisting of polyethylene glycols andpolyalkanolamines. Other features and advantages of the invention willbecome apparent from the following description and the accompanyingclaims.

The plasticizers of this inventionmay be intro du'c'e'd into the spongematerial either in the form of a solution or as substantially anhydrousliquids. When a solution is used an aqueoussolution is preferred inwhich the sponge is soaked so as to absorb the maximum amount ofsolution and then. the excess solution is removed. When the plasticizersare added in substantially anhydrous form, the liquid plasticizer isheated and the sponge is immersed in the heated plasticizer for from afew seconds to several hours depending upon the temperature employed.The sponge is thenreinoved from the plasticizer and the excessplasticizer is removed.

Among the suitable plasticizers that have been discovered are diethyleneglycol, triethylene glycol, tetraethylene glycol, polyethylene glycolhave ing a molecular weight of about 209, other polyethylene glycolshaving molecular weights of more than 200, triethanolamine and methyldiethanolamine. The plasticizers may be used alone or in combinations oftwo or more. When the substantially anhydrous plasticizer is employed,the liquid plasticizer is preferably heated at a temperature betweenabout 37 to C. At the higher temperatures care must be used that thesponge is not immersed for too long a time, as ordinarily only a fewseconds is required at the high temperatures. A temperature of about 50C. is preferred.

Any amount of plasticizer desired may be used so long as a plasticizingeffect is achieved. In general, the sponge should contain approximately50% of the anhydrous plasticizer by weight of the dry sponge material.In actual practice, it has been found that excellent results have beenachieved when at least 30% of the plasticizer is employed by weight ofthe dry sponge material. Ordinarily not more than about 100% isrequired, but in some instances it may be advisable to use more. Underconditions of high humidity, the minimum amount may be reduced below30%. For example, 20% is satisfactory if the relative humidity of theatmosphere surrounding the sponge is at least 85-90%.

The following examples illustrate methods of practicing this invention:

Example 1 liquid. The sponge material retained about 6 grains of thesolution and remained flexible in the atmosphere.

Example 2 A. partially formalized polyvinyl alcohol sponge madeaccording to the above application was soaked overnight in triethyleneglycol at 50 C. At the end of this time, the excess plasticizer wasremoved by squeezing the sponge. This sponge remained soft and flexiblewhen exposed to air at room temperature.

Example 3 A portion of the sponge material Was soaked in a 30% by weightaqueous solution of triethanolamine. After the excess solution had beenremoved by squeezing, the sponge remained soft when exposed to air atroom temperature. The sponge was found to contain 60% triethanolamine,calculated as anhydrous amine and based on the weight of the dry sponge.

Example 4 A portion of the sponge material was soaked in a 30% by weightaqueous solution of methyl diethanolamine. After the excess solution hadbeen removed by squeezing, the sponge remained soft when exposed to airat room temperature. The sponge was found to contain 60% methyldiethanolarnine, calculated as anhydrous amine and based on the weightof the dry sponge.

Of the plasticizers described herein, the polyethylene glycols arepreferred, and especially triethylene glycol. Diethylene glycol,triethylene glycol, tetraethylene glycol and other polyethylene glycolshaving a molecular weight of at least 200 may be employed. It ispreferred, however, that the polyethylene glycol contain not more than 8ethylene groups in the molecule.

Polyhydric alcohol plasticizers for partially formalized polyvinylalcohol sponges are disclosed and claimed generally in my copending 4application serial No. 116,642, filed September 19, 1949.

Having described my invention as related to various embodiments of thesame, it is my intention that the invention be not limited by any of thedetails of description unless otherwise specified, but rather beconstrued broadly within its spirit and scope as set out in theaccompanying claims.

I claim:

1. The method of making a soft, resilient sponge material havinginterconnected pores by reacting polyvinyl alcohol and formaldehyde,which comprises: providing an aqueous solution of formaldehyde,polyvinyl alcohol containing less than 10% residual hydrolyzablematerial in the molecule, an acid catalyst in which the acid functionalgroup is inorganic and having a dissociation constant of at least 10 anda frothstabilizing wetting agent soluble in and substantially stable tosaid solution; forming a substantially stable and homogeneous froth withsaid solution stabilized with the wetting agent; reacting the polyvinylalcohol and formaldehyde in the solution thereby causing gellation andsolidification of the froth with the production of interconnected poressimultaneously with the progression of the reaction, the froth beingformed prior to appreciable reaction between the polyvinyl alcohol andthe formaldehyde; stopping said reaction when approximately 35-80% ofthe hydroxyl groups of the polyvinyl alcohol have been reacted with theformaldehyde; whereby a sponge material is formed impregnating saidsponge with a liquid including a mem ber of the class consisting ofsubstantially anhydrous polyethylene glycols and polyalkanol' aminesheated to a temperature of up to about 100 C. and aqueous solutions ofsaid amines, and removing excess of said liquid until there remainsdeposited on said sponge about 20-100% of said liquid based on the dryweight of the p e.

2. A method according to claim 1 in which said liquid is triethyleneglycol.

3. A method according to claim 1 in which said liquid is a polyethyleneglycol having a molecular weight of approximately 200.

4. A method according to claim 1 in which said liquid istriethanolamine.

5. A method according to claim 1 in which said liquid is diethyleneglycol.

6. A method according to claim 1 in which said liquid is methyldiethanolamine.

7. A sponge material prepared by the method of claim 1 and in which saidliquid is a polyalkanolamine.

CHRISTOPHER LUMLEY WILSON.

References Cited in the file of this patent UNITED STATES PATENTS

1. THE METHOD OF MAKING A SOFT, RESILIENT SPONGE MATERIAL HAVINGINTERCONNECTED PORES BY REACTING POLYVINYL ALCOHOL AND FORMALDEHYDE,WHICH COMPRISES: PROVIDING AN AQUEOUS SOLUTION OF FORMALDEHYDE,POLYVINYL ALCOHOL CONTAINING LESS THAN 10% RESIDUAL HYDROLYZABLEMATERIAL IN THE MOLECULE, AN ACID CATALYST IN WHICH THE ACID FUNCTIONALGROUP IS INORGANIC AND HAVING A DISSOCIATION CONSTANT OF AT LEAST 10-2AND A FROTHSTABILIZING WETTING AGENT SOLUBLE IN AND SUBSTANTIALLY STABLETO SAID SOLUTION; FORMING A SUBSTANTIALLY STABLE AND HOMOGENEOUS FROTHWITH SAID SOLUTION STABILIZED WITH THE WETTING AGENT; REACTING THEPOLYVINYL ALCOHOL AND FORMALDEHYDE IN THE SOLUTION THEREBY CAUSINGGELLATION AND SOLIDIFICATION OF THE FROTH WITH THE PRODUCTION OFINTERCONNECTED PORES SIMULTANEOUSLY WITH THE PROGRESSION OF THEREACTION, THE FROTH BEING FORMED PRIOR TO APPRECIABLE REACTION BETWEENTHE POLYVINYL ALCOHOL AND THE FORMALDEHYDE; STOPPING SAID REACTION WHENAPPROXIMATELY 35-80% OF THE HYDROXYL GROUPS OF THE POLYVINYL ALCOHOLHAVE BEEN REACTED WITH THE FORMALDEHYDE; WHEREBY A SPONGE MATERIAL ISFORMED IMPREGNATING SAID SPONGE WITH A LIQUID INCLUDING A MEMBER OF THECLASS CONSISTING OF SUBSTANTIALLY ANHYDROUS POLYETHYLENE GLYCOLS ANDPOLYALKANOLAMINES HEATED TO A TEMPERATURE OF UP TO ABOUT 100* C. ANDAQUEOUS SOLUTIONS OF SAID AMINES, AND REMOVING EXCESS OF SAID LIQUIDUNTIL THERE REMAINS DEPOSITED ON SAID SPONGE ABOUT 20-100% OF SAIDLIQUID BASED ON THE DRY WEIGHT OF THE SPONGE.